A study released by the Archives of General Psychiatry says children whose mothers took antidepressants during pregnancy are twice as likely to be autistic.

The study suggests that the class of antidepressants known as selective serotonin reuptake inhibitors (SSRIs) may be risky early on in a pregnancy, CNN reported.

According to the small study, which included fewer than 200 children with autism spectrum disorder (ASD), children exposed to the drugs during the first trimester were nearly four times as likely to develop an ASD than unexposed children.

The study did not directly prove that taking the antidepressants, which include Zoloft and Prozac, directly causes ASD. The findings must be confirmed in larger studies, experts on prenatal and mental health say.